Tunable magnetron



1 I J. L. H. JONKER ETAL 2,899,603

\ TUNABLE MAGNETRON Filed July s, 1956 r 2 Sheets-Sheet 1 IN V EN TOR. JmMLapzmaK/m Dmm Aug. 11, 1959 J. L. H. JONKER ETAL TUNABLE MAGNETRON Filed July 5, 1956 2 Sheets-Sheet 2 aqJWi vm/ IR aime/7" 0 VA is AGENT 2,899.60; TUNABLE .MAGNETRON Johan Lodewijk Hendrik Jonker and, Gerrit de Vries,

Eindhoven,fNetherlands, assigiiors, by mes'ne assignments, to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Application July 3, 1956, Serial No .,'59'5,6 2 (l Claims priority, application Netherlands July 4, 1955 '5 Claims. (Cl. 31 5-6951) This invention relates to magnetrons and particularly to. means for tuning magnetrons over a relatively wide range of frequencies.

The invention comprises a cylindrical electrode system consisting of a central tubular cathode surrounded by a plurality of anode segments evenly spaced in a circle about the cathode in a manner well known in the magnetron art. Adjacent pairs of anode segments are connected together by flexible U-shaped conductors. Alternate ones of said anode segments are mechanically linked together for example by a first ring-shaped member attached to one leg of each U-shaped conductor and the remain ing anode segments are linked together by a secondmenther which is also preferably in the form of a ring and is attached to the other leg of each U-shaped conductor. The electrical circuit formed by this arrangement consists of a plurality of series-tuned circuits in each of which the U-shaped conductor is the inductiveelement and the capacitance between adjacent anode segments of adjacent U-shaped conductors is the capacitive element. Alternatively, the proximal anode segments at tached to adjacent U-shaped conductors may be connected by a series-tuned circuit comprising a similar, additional U-shaped conductor each end of which is capacitively coupled to the anode segment on eitherside. By virtue of the series connection of the elements the number of possible modes of oscillation issmaller than is the case in the usual parallel connection of the segments in magnetrons of the prior art.

In order to tune the. magnetron of the present invention one of the mechanical linkage members is rotated about the common axis of the electrode system with respect to the other mechanical linkage member so that the sides of the U-shaped conductors are either drawn closer together or spread farther apart, depending on therelative direction of rotation. In this way the parameters of all of the series-tuned circuits are varied simultaneously. The frequency change thus accomplished can extend over a broader band of frequencies than is the case for the usual magnetron tuning without jumping from one mode of oscillation to another.

The primary object of the invention is to provide an improved tunable magnetron the operating frequency of which may be varied over a relative broad band of he quencies without shifting the mode of oscillation. Other objects will follow from the specification together with the drawing in which:

Fig. 1 shows a perspective view of one arrangement of the anode segments, U-shaped conductors, and mechanical linkage members according to the invention;

Fig. 2 is a cross sectional view of magnetron incorporating the arrangement of Fig l Fig. 3 is a top view of the arrangement of Fig. 1 showing the mechanical effect of rotation of one of the conductive connections relative to the other;

Fig. 4 is a view, corresponding to a part of Fig. l, of a modification of the invention.

In Fig. 1 the reference characters 1-12 indicate anode te rates atcnt Patented Aug. 11, 1959 segments which are spaced around .the periphery of a circle. Half of the anode segments, that is, those, with odd referenceflcharacters, are.v attached to a ring-shaped mechanical linkage member 13, which may be either conductive 01" non-conductive, and the other half of the anode segments, that is, thosewith even reference characters, are attached to a second ring-shaped mechanical linkage member 14. Adjacent pairs of anode segments are connected together by U-shaped conductors 15-20 of which conductor15 connects anode segments 1 and 2, conductor 16 connects segments Sand 4, andso on.

The electrode arrangement of Fig. 1 is incorporated into a complete magnetron, a cross sectional view of which appears inFig. 2 in which parts similar to those in Fig. I bear identical reference characters. In Fig. 2 the lower ring 13 is firmly attached by means of a plurality of pins' 21 to the bottom wall 22 of the magnetron and the upper ring 12 is supported by a plurality of arms 23 joined together to a shaft 24 which is journaled in an internal projection 25 of the upper wall 26 of the magnetron.

In order, to rotate the upper ring 14 within the evacuated magnetron envelope a shaft 27 is provided and is attached to one of .the arms 23. Thisshaft extends through anopening in the side Wall of the magnetron and terminates in a bellows 28 which is hermetically sealed to the sidewall around the opening. A tuning adjustment screw 2? presseson the bellows, and movement of the screw in or out causes a corresponding movement in or out of the shaft 27'which in turn rotates the arm 23 aboutthe central shaft 24 thus rotating the upper ring 14 with respect to the'lower ring 13. The screw 29 is carried in a chamber 30 attached in the side wall of the magnetron and is located by a lock-nut 31.

At the centre of the. electrode system is a cylindrical cathode 32 and atone side of the electrode system is a pair of outputterminals 33,. or antennae, connected respectively to the lower and upper rings 13 and 14.

The tuning of the electrode system is illustrated in Fig. 3 in which a capacitor 34 is shown in dotted form to indicate the capacitance between adjacent anode segments 6 and 7 and an inductance 35is also shown in dotted form to indicate the inductance of the U-shaped conductor 17. It has been found that the relative spacing between adjacent anode segments connected to the ends of one U-shaped conductor should preferably be spaced apart by a distance substantially four times the distance between anode segments connected to 'the proximal ends of adjacentIU-shaped conductors. This relation is indicatedby the anglefl between anode segments 6 and 7 and the angleis 40 between anodev segments 7. and 8. in this way the inherent capacitance in parallel with the inductance of each U-shaped conductor will be reduced to the point where it no longer has a substantial elfect on the tuning of the system. It should be noted that the electric field between the widely spaced anode segments, for example segments 5 and 6 or 7 and 8, coacts with the electrons, whereas the field between the closely spaced anode segments such as segments 6 and '7 is of relatively minor importance.

Fig. 3 shows in dotted outline the position of the various U-shaped conductors when the upper ring 14 is rotated in the direction of the arrow 36 relative to the lower ring (not shown in this figure). Rotation of the upper ring 14 as indicated moves all of the closely spaced anode segments, for example segments 6 and 7, farther apart, thereby reducing the capacitance 34 and increasing the frequency. It should be noted that the relative movement of the upper ring 14- with respect to the lower ring may actually be very slight.

Fig. 4 is a fragmentary view showing a modification of the electrode arrangement of Fig. 1. In Fig. 4 the anode segments are identified by reference characters 106-108 and are in the form of strips bent to form sections of a cylinder. Strips 107 and 108 are joined by a U-shaped conductor 118 which is attached by a tab 37 to a ring 113 and by another tab 38 to a second ring 14. As shown, the rings 113 and 14 are at the same end of the cylindrical electrode system but may, if desired, be placed at opposite ends as are conductive connections 13 and 14 in Figs. 1- and 2. In either case rotation of one of the rings, for example 14 with respect to the other ring 113, moves the two sides of the U-shaped conductors, such as conductor 118, with respect to each other.

The embodiment of Fig. 4 has an additional number of U-shaped conductors, two of which are indicated by reference characters 39 and 40. These latter U-shaped conductors are also connected to the rings 113 and 14, in the same way as is the U-shaped conductor 118. That is, con ductor 39 is connected to ring 14 by means of a projection 41 and to ring 113 by means of a projection 42. The outer ends of the U-shaped conductor 39 and 40 are bent back to form portions of a cylinder coaxial with that formed by anode segments 106-108. By virtue of this arrangement the gap between each of the anode segments, such as segments 106 and 107, may be made substantially equal to the other such gaps, for example between segments 107 and 108. Segments 106 and 107, instead of being directly capacitively coupled as are segments 6 and 7 in Fig. 1, are capacitively coupled to bent-back tabs 43 and 44, respectively, at the ends of the U-shaped conductor 39 to form tuning capacitors which are joined by the inductance of the U-shaped conductors 39 in one seriestuned element of the whole series-tuned electrode system. The only gaps presented to the electrons are operating gaps, the fields of which coact with the electrons. As in the embodiment in Fig. 1, tuning is accomplished by rotating the rings 14 and 113 with respect to each other. In the embodiment of Fig. 4 not only do the ends of U- shaped conductor 118, which are connected to the anode segments 106 and 107, move with respect to each other but also the ends of U-shaped conductors 39 and 40 move with respect to another end in such direction as to change the capacitance between tabs 43 and 44 and anode segments 106 and 107 and vary the tuning of the electrode system.

Although this invention has been described in terms of specification embodiment it will be obvious to those skilled in the art that modification may be made within the scope of the following claims.

What is claimed is:

1. A tunable magnetron comprising a cylindrical cathode; an even number of U-shaped flexible conductors arranged in a circle coaxial with said cathode, the free ends of said U-shaped conductors constituting anode segments said cathode and said anode-segments making up an electrode system; a pair of superposed coaxial rings of substantially the same diameter; a mechanical connection between one of said rings and alternate ones of said anode-segments respectively; a mechanical connection between the other of said rings and the remaining ones of said anodes, respectively; and means to rotate one of said rings with respect to the other of said rings to vary simultaneously the spacing between the ends of each of said U-shaped conductors to tune said electrode system.

2. A tunable magnetron according to claim 1 in which the spacing between the ends of each of said U-shaped conductors is of the order of four times the spacing between the proximal ends of adjacent U-shaped conductors.

3. A tunable magnetron according to claim 1 in which one of said rings is at each end of said electrode system.

4. A tunable magnetron according to claim 1 comprising in addition a second plurality of U-shaped flexible conductors, one of said latter U-shaped flexible conductors being disposed between each pair of the first-named plurality of the U-shaped flexible conductors and capacitively coupled to said pair, one side of each of said second plurality of U-shaped conductors being connected to one of said rings and the other side of each of said second plurality of U-shaped conductors being connected to the other of said rings.

5. A tunable magnetron comprising a cylindrical cath- 3 ode; an even number of U-shaped flexible conductors arranged in a circle coaxial with said cathode, the free ends of said U-shaped conductors being bent back to form sections of a cylinder and constitute anode segments; a second plurality of U-shaped conductors disposed between adjacent ones of said first-named plurality of conductors,

each end of each of said second plurality of conductors being bent back to form a section of a second cylinder coaxial with said anode segments and being capacitively coupled to one of said anode segments respectively; a first ring attached to a corresponding side of each of said U-shaped conductors; and a second ring coaxial with and substantially the same diameter as said first ring connected to the juxtaposed side of each of said second plurality of U-shaped conductors; and means to rotate one of said rings with respect to the other to vary oppositely the spacing between proximal sides of all of said U-shaped conductors simultaneously.

References Cited in the file of this patent UNITED STATES PATENTS 

